ON LA~RVM OF LINGULA AND PELAGODISCUS (DISCINISCA). 65 



that of Lingula, but the contents of the cells, as seen in life, are not so refringent. 

 The intestine, which is not ciliated, issues from the ventral wall of the mid-gut near 

 the middle line and a little anterior to its hinder margin (fig. 11). It runs towards 

 the right and is at first narrow, but becomes wider as its enters the postero-lateral 

 corner of the body-cavity, where it is dilated into a sub-spherical sac from which the 

 narrow terminal portion runs anteriorly and slightly laterally to open on the body- 

 wall ventral to the pigment-spot and near the postero-lateral margin of the right 

 anterior occlusor. The mid-gut is pale yellow in colour, and scattered through the 

 " liver "-cells there is a considerable amount of brownish pigment. 



The larva feeds on unicellular algse ; spherical algse and a few diatoms are 

 present in the gut. 



The ccelom is not spacious ; there are, however, obvious portions of the coelom 

 in the postero-lateral regions of the body and a connecting transverse cavity 

 posterior to the mid-gut. Unfortunately, I have no observations on the ccelomic 

 fluid or its contents in life. 



All the specimens possess a pair of ccelomoducts (nephridia), which have not 

 hitherto been observed in the free-swimming larvae of any Discinid. The funnel of 

 each ccelomoduct is situated on the ileo-parietal band about the level of the posterior 

 margin of the mid-gut ; its opening is directed posteriorly and rather towards the 

 middle line (fig. 11). The funnel leads into a slender tube which can be traced 

 forwards a little more than half way along the lateral margin of the occlusor muscle 

 to its opening into the mantle-chamber. The total length of the ccelomoduct is, 

 about 70-9 0/i,. The funnel appears in section as a double series of cells with deeply 

 staining nuclei, representing the two lips, between which is a narrow lumen. The 

 dorsal lip is slightly longer than the ventral. The rest of the duct is lined with a 

 flat epithelium and ensheathed with a very thin ccelomic epithelium. The lumen of 

 this portion is widest about the middle of its length, where it may attain a diameter 

 of 5/a, but is usually much narrower (2-3//,). 



The larvse described above correspond exactly with those studied by Fritz 

 Muller, and they agree with those described by Drs Blochmann and Yatsu except 

 that their specimens had no pigment-spots ("eye-spots"). This difference, in view 

 of the close agreement in other respects, should probably not be considered as 

 significant ; it may be merely a local variation. 



Professor Blochmann has adduced cogent evidence for regarding the larvse 

 described by Muller and himself as belonging to Pelagodiscus (Discinisca) 

 atlanticus. The identity of my larvse with those of Muller and Blochmann 

 seems so clear that they may safely be referred to the same widely distributed 

 species, the range of which is now extended into the Indian Ocean. There is, so 

 far as I am aware, no record of adults of P. atlanticus from the Indian Ocean, and 

 the nearest record of the species is that of Professor Blochmann, whose larvse were 

 taken off the island of Bintanw. 



